The present invention relates specifically to softballs that are associated with the game of softball.
The softball of the instant invention has a circumference of approximately 12 inches (30.5 cm), a weight of 177 to 198 grams and a coefficient of restitution of 0.487. The majority of the prior art softballs are covered with a leather cover that is formed from two pieces that are sewn together by hand with herringbone stitching. The stitching tends to form ridges which affect the aerodynamics of the ball and facilitate throwing of pitches which break, curve or slide under their trajectory.
U.S. Pat. No. 4,498,667 to Tomar describes a process for forming rubber or vinyl coated baseballs or softballs in which thermoplastic rubber or plasticized vinyl resin is injected into a mold cavity.
U.S. Pat. No. 4,462,589 to Morgan discloses a safety ball formed with a soft closed-cell plastic foam core. The ball has a type A durometer of less than 60 and preferably in the range of about 25 to 45.
U.S. Pat. No. 3,976,295 to Heald discloses a ball formed with a spherical core of polyurethane foam covered with a thin winding of cotton yarn and with a hand stitched outer cover.
U.S. Pat. No, 4,529,200 to Miller et al describes a game ball for use as a conventional baseball or softball having a conventional core of cork and a plastic shell covering the core in lieu of conventional windings.
U.S. Pat. No. 4,572,507 to Hubbert et al discloses a game ball in which the core consists of a thermoplastic resin center and a winding which is heat fused thereto. The ball is covered with a two-piece stitched cover.